Polimer Automotif

7/26/2019 Polimer Automotif

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Proven lightweighting technologyfor automotive applications

MuCell


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T

he MuCell microcellular foam injection molding process for

thermoplastics materials provides unique design flexibility and

cost savings opportunities not found in conventional injection

molding. The MuCell process allows for plastic part design with

material wall thickness optimized for functionality and not for the

injection molding process. The combination of density

reduction and design for functionality often results in material

and weight savings of more than 20%.

By replacing the pack & hold phase with cell growth, lower stress

parts are produced which have enhanced dimensional stability

and substantially reduce warpage. Cell growth also results in the

elimination of sink marks.

Unlike chemical foaming agents, the physical MuCell process

has no tempertature limitation and does not leave any chemical

residue in the polymer; making consumer products perfectly

suitable for recycling within the original polymer classification

and allowing re-grind material to reenter the process flow.

The numerous cost and processing advantages have led to

rapid global deployment of the MuCell process in automotive,

consumer electronics, medical device, packaging and

consumer goods applications.

MuCell Molding Technology

The most significant plastic processing

innovation in the last 20 years

Lightweighting 8-12% material density reduction

20 - 30% total part weight reduction

by designing for MuCell

Sustainability Reduced petroleum based material consumption

Reduced molding machine energy consumption

Ability to re-grind / re-use molded parts

Reduced carbon footprint versus solid molding

Reduced Costs Reduced resin consumption

Faster molding cycle time

Increased yields

Smaller molding machine Use of lower cost filled polyolefin material

Design Freedom Thin to thick wall flow

1:1 wall thickness rib structure

Material where needed for function versus flow

Improved dimensional stability

Less warpage


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MuCell/ Polymer Value Match

During plasticization,precisely metered amounts

of supercritical fluid (SCF),typically Nitrogen or CO2,

are introduced into thepolymer through injectorsmounted on the plasticizingbarrel.

Injection of polymer into moldcavities. Cells start to nucleateonce exposed to lower pressurein the mold cavity. Moleculardispersion of SCF providesfor a homogeneous closed cell

structure with a solid skin layer.

Homogeneous mixing and

disbursing of the supercriticalfluid into the polymer throughthe specially designed mixing

section of the plasticizingbarrel, creates a single phasesolution of SCF and moltenpolymer.

Low pressure filling of moldcavities. Pack & hold phaseis replaced by controlled cell

growth, which ceases oncethe mold cavity is filled. Cellgrowth results in a uniform

pack pressure throughout themold cavity.

Virtually all polymers will develop a cellular structure with the MuCell process except for LCP. Filled materials tend to offer the

greatest value as fillers act synergistically with the supercritical fluid to provide the best combination of weight reduction and cycle

time reduction. Unfilled amorphous materials also foam very well and can provide good weight reductions but with less cycle time

benefits than filled materials. High temperature materials such as PEEK, PEI and PSU also provide significant cost reduction based

on material price.

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Good Value Great Value

HDPE Acrylic HDPE Glass

PVC HIPS PVC PP Glass

TPE HIPS TPE PPO Blends

ABS PA6/6.6 Unfilled ABS PSUTPV GPPS TPV PIE

PP Unfilled POM PP Unfilled PA6/6.6 Glass

TPO TPO PBT Glass

F O U R T E C H N O L O G Y S T E P S


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Solid

Molding

MuCellInjection Pack & Hold

Cooling Motions

B

y replacing the tradition pack & hold phase of the solid

molding process with cell growth, the MuCell process

allows for uniform and locally applied pack pressure through cell

growth. This allows part design to be optimized with material

thickness in those areas that require strength and reduced wall

thickness in areas that are not structural. Gate locations are then

placed in the thin cross sections for optimized filling patterns

while allowing the cell growth to provide packing in the thicker

cross sections at the end of fill.

Using the same principle, nominal wall thickness can be reduced

while using thicker ribs to meet structural requirements. The

cell expansion will eliminate sink marks and the cell structure

will prevent the formation of vacuum (shrink) voids. Rib to wall

thickness ratios of 1:1 can be used with the MuCell process.

T Y P I C A L C Y C L E T I M E R E D U C T I O N W I T H M U C E L L

A part molded with the MuCell

process has a solid skin layer andmicrocellular foamed core which is aclosed cell structure. The cell growthis more effective at packing the partthan the solid pack phase whichallows for increased rib to nominalwall thickness without sink marks. Inmost cases, it is possible to produce asink free part with a rib thickness

equal to the nominal wall thickness.

Recommended

injection with MuCell

Injection in solid

(with MuCell still possible)

Differences in Wall Thicknesses

Conventional Design MuCell Design

Wall to rib ratio 1:1 possible

Filling from thin to thick

Total 30 Seconds

Total 22 Seconds

3 sec 4 sec 17 sec

1.5sec

0.5sec

14 sec 6 sec

The MuCell Application Advantage:

The freedom to design for functionality

and not for plastic process limitations


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MuCell Molding Technology

The complete process solution providing for lighter and

more accurate plastic parts at lower production costs

Climate Control Bezel | Material: Glass filled ABS Elimination of sink marks

1:1 ribs to nominal wall

Machine clamping force reduced from 250 tons to 75 tons

23% cycle time reduction

10% weight reduction

Airbag Cover | Material: TPO

Uniform shrinkage across different wall thicknesses, enhanced dimensional stability Elimination of readthrough on the tear seam

Improved living hinge functionality down to temperatures of minus 30C

Weight / material savings of 9%

Engine Cover | Material: Appearance Grade GF PA6 7% weight reduction

Improved flatness

Black sections molded in color

Mirror Assembly Case Frame | Material: 50% GF PBT 10% cycle time reduction (5 seconds)

10% (84 Gram) weight reduction

Reduction of warpage

Machine clamping force reduced from 650 tons to 420 tons

Cam Cover | Material: Glass Filled PA Machine clamping force reduced from 500 tons to 350 tons

Improved cycle times (allows for simultaneous production and assembly process)

Lighter part and improved flatness

Maintain solid surface apprearance


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A U T O M O T I V E A P P L I C A T I O N S

HVAC System | Material: 20% talc filled PP 9-12% weight reduction

10-15% cycle time reduction

Flatter parts and better fit

Improved long term reliability and better sealing

Front Lamp Housing | Material: PP GF10 T20

9% weight reduction Machine clamping force reduced by 50%

Improved screw boss behaviors by elimination of voids

(as compared to conventional molding)

Improved material flow and easier cavity filling

Instrument Panel | Material: LGF PP 8% weight savings

20% cycle time reduction

Machine clamping force reduced by 42%

Significantly reduced warpage

Fan Shroud | Material: PA 66 Glass filled, PP Glass filled Weight / material reduction of 11%

Cycle time reduction of 30%

Machine clamping force reduced by 50%

200% improvement in fatigue resistance

Cpk values improved >50%

Door Module | Material: Glass filled PP Expansion molded for increased stiffness

Selective expansion from 2 mm to 3 mm

40% weight reduction


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Field retrofit of existing injection molding

machines by qualified Trexel technicians. The

upgrade consists of a new, MuCell capable

plasticizing unit, positive screw position control,

installation and training.

For new injection molding machine applications, the

following licensed Trexel OEM partners can provide a

turnkey MuCell injection molding system.

The MuCell capable injection molding machine consists of Nitrogen or CO2 supply, a SCF metering and

control system, and a specialized plasticizing unit including positive screw control and a shut off nozzle.

The technology can be easily integrated into new (OEM Model) or existing (MMU Model) molding machines:

M O D U L A R M U C E L L U P G R A D E ( M M U ) O E M S Y S T E M

I M P L E M E N T I N G T H E M U C E L L P R O C E S S

Front non-return valve

Back non-return valve

Shut off nozzleSCF injector SCF metering system


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Trexel, Inc.100 Research DriveWilmington, MA 01887 USA

Tel.: 781-932-0202www.Trexel.com

E U R O P E C H I N A J A P A N K O R E A N O R T H A M E R I C A A U S T R A L I A

HEADQUARTERS

SUBSIDIARIES

TECHNICAL CENTERS

As a leader in providing lightweighting solutions to

the plastics injection molding industry, Trexel, Inc. has

extended its MuCell processing solution to blow

molded automotive components.

There are several highly desirable attributes of foamed

versus solid blow molded parts:

Weight savings

The microcellular material structure improves

thermal insulation and acoustical properties

The MuCell technology, a physical foaming process, also has

several advantages over the use of chemical foaming agents:

No chemical reaction at narrow processing window

No chemical additive residue in final parts

MuCell foamed parts can be recycled in their

original polymer designation; the process does not

alter the chemistry of the polymer

T

he MuCell Microcellular foaming technology was originally

conceptualized and invented at the Massachusetts Institute

of Technology (MIT) and in 1995 Trexel was granted an

exclusive worldwide license for the further development and

commercialization of the technology. Today, Trexel is the exclusive

provider of the MuCell microcellular foam technology for

injection molding and maintains an extensive global patent

portfolio. Trexel provides world-class engineering support,

training and other design and processing services, as well as the

equipment and components integral to the MuCell process.

From the global headquarters in Boston, Massachusetts, Trexel

operates a state of the art plastics processing developmentlaboratory, supporting plastics processors with the definition

and implementation of leading and differentiating plastic

molding technologies.

In support of a global client base, Trexel operates subsidiaries

in Europe, Japan and Southeast Asia with competent plastics

processing engineering capabilities. Trexels worldwide

subsidiaries are augmented by a network of competent

independent representatives and distributors.

About Trexel

The exclusive provider of the MuCell Microcellular

Foam Injection Molding Technology

MuCell blow molded polyethylene air duct with

41% density reduction compared to solid.

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Polimer Automotif